Frame for transits and similar instruments



Aug. 22,1933. w EGY ETAL X 1,923,193

FRAME FOR TRANSITS AND SIMILAR INSTRUMENTS Filed Aug. 31, 1931 Y '9 5 7 ii 0' 34% 51 23 213M544 25 I attorneys Patented Aug. 22, 1933 UNITED STATES FRAME FOB. TRANSITS AND SIMILAR INSTRUIVIENTS Willard L. Egy, Charles 1. Day, and Charles E.

Smart, Troy,v N. Y., assignom to W. & L. E. Gurley, Troy, N. Y., a-Corporation of New York Application August 31, 1931. Serial No. 560,514

9 Claims.

This invention relates to frames for transits and similar instruments.

. The object of the invention is to produce a I frame which may besimply constructed and one which is subject to the minimum distortion as the result of differential expansion of members of the trai The desired results are secured in a remarkable degree and are attributable in part at least to P the symmetrical construction of the frame; to the fact that the frame members are essentially solidaof revolution; and to the fact that the frame members are devoid. of flanges and reentrant angles, and hence, areas nearly uniform in'cros's section as is practicable.

Another feature of importance to the final resuit is the fact that one of thetwo component parts of the frame is so connected to the other that it is stressed in hoop tension, and the other I is subject to uniform radial compression. Hence, there are nointernal stresses tending to induce distortion. y

The ideal transit frame would be all in one 5 cal requirements for the metal forming the verticalspindle and the requirements imposed by available commercial methods for producing the rather complicated form of telescope standard, are not at present favorable to the use of a single material. Consequently, in practice, the use of a composite construction is desirable. One feature of the invention is the development of a composite structure in which separately formed component are permanently so connected as to be subjected to the minimum internal strains, and

in which such internal strains as necessarily exlst, are balanced, induce a stable condition, and, therefore, donot contribute to distortion. I

indicating the utility of the invention, it

' may be mentionedthat it is well known that on a day when fast moving clouds periodically obscure the arm, a transit, if sighted on a distant target,

will waver appreciably from the target, as the '5 result of differential expansion of the frame. A

transit having a frame constructed according to the disclosure of the present invention, does waver in a degree, but the amount is only a small fraction of that encountered with the best prior m art instruments.

The invention will now be described in connection with the accompanying drawing, in which: Fig. 1 is a perspective view of the complete frame. V Fig. Zis a side elevation thereof. Fig. 3 is a front elevation.

piece and of homogeneous material, but the physi- Fig. 4 is a plan. v I

Fig. 5 is a fragmentary radial section indicating the preferred composite construction. 7

Referring first to Figs. 1 to 4 inclusive, the vertical spindle on which the-frame is mounted, is of familiar form, and is indicated generally by the numeral 10. The spindle 10 is provided with tapered bearing surfaces 11 and 12 and. relief grooves 13 and 14. The bearing surfaces are intended to turn in the usual quill which carries the horizontal limb. The quill and horizontal limb are not features of the present invention and may follow established standards. Hence, they are not shown in the drawing. The shoulder. 15, in the assembled transit, rests on the upper end of the quill, as usual, to limit the insertion of the spindle into the quill, and thus ensure'a close but freeturning fit.

Supported on the upper end of the vertical spindle is the base plate, generally indicated at 16. This, in a unitary frame, would be in one piece,

as indicated in Fig. 1. For ease of manufacture,

the base plate is preferably composed of two parts, as indicated in Fig.5. As shown in Fig. 5, there is a hub portion or head 16 formed integrally with the spindle 10, and an, annulus 16 formed integrally with the telescope standards, hereinafter described. I

Preferably, the part 10, 16, is a drop forging and desirably, but not necessarily, may be composed of a "strong aluminum alloy, heat treated and artificially aged. Suitable alloys and treatment are described in the patent to'Archer and Jeifries, No. 1,472,739,, granted October 30, 1923. The annulus 16 and the standards may be variously formed and of various different materials, but a convenient method is casting, using an aluminum alloy. This may be for example an aluminum-copper alloy containing about 5% copper. The parts 16 and 16" are threaded together, as indicated at 17, a shoulder 18 limiting the threaded engagement. In'assembling the parts,

the annulus 16 is preferably heated somewhat and the hub 16 is preferably chilled. The di- 10o mensional tolerances are close, so' that when the parts are screwed together, they seize, and cannot be separated without destruction' of one or both.

' The resultant frame has the essential characteristics of unitary construction, and can be sucm5 cessfully machined as. a unit. The annulus 16 is stressed in hoop tension, so that it is in a balanced state of stress favorable 1 to stability of form. The head 16 is in a state of radial compression and, hence, stable.

The flange 19 is intended to carry verniers, no

which are not features of the present invention, and, hence, are not illustrated.

The telescope standard structure is integral with the base plate 16, and in the composite construction shown in Fig. 5, is integral with the annulus 16 I I i The standard structure is substantially a solid of revolution with certain parts cut away to produce an open-work frame. It is concentric with the annulus and spindle 10 and with the base plate generally, a condition which minimizes any tendency to distortion.

The frame elements of the standard structure are a pair of diametrically opposed loop-shaped (generally elliptical) uprights 21 and intervening bowed interbraces 22. The loop-shaped uprights 21 have filleted bases 23 atthe annulus lfi and the bowed interbraces 22'are connected at their ends with and merge into the uprights-21 and at their middles have filleted bases 24 connected with the annulus'lfi At the tops of the uprights 21 are bosses 25 which receive the telescope trunnion bearings generally indicated at 26. The construction of the bearings 26 is not a feature of the invention and anysuitable bearing might be used to define the usual horizontal axis, 1. e., anaxis perpendicular to and intersecting the axis of the spindle 10.

The frame structure 21, 22 has a number of important characteristics. It is a solid of revolution with reference to-the axis of spindle 10,

i-.e., the outer surface2'7 isa surface of revolution about the axis of spindle 10, preferably a cone (as in the example illustrated), and the major (or lower) portion of the inner surface as indicated at 28 is also a similarsurface of revolution about the same axis. The remaining surfaces 29, 31, 32 and 33 are, in the example illustrated, ruled surfaces whose generatrices'are either parallel with the horizontal axis defined by bearing 26 or else perpendicular'tosuch axis and to the axis of spindle 10. This is not important and may be departed from without afiecting the character of the frame for strength and stability. The form is well adapted to profiling operations and has been found satisfactory. g

The constructiondefined has advantages both from the standpoint of manufacture and from the more important standpoint ofmaintained accuracy and stability under varying conditions.

While a cast frame hand' finished is sufiiciently accurate in form for many uses, greater stability may be had by machining the standards to precise form and the frame is well adapted for machine finishing." In such' casefthe sur faces 27 and 28 are turned or ground on centers defining the axis of spindle 10., The remaining surfaces 29, 31, 32, and 33 are finished by profiling operations. I 7 e The transit frame structure is so'designed that the elements 21 and 22 have,as nearly as practicable, uniform cross sectional areas,'free from flanges and reentrant angles. Consequently they respond as nearly uniformly as is possible to temperature changes. In effect, therefore, the frame is so formed as to be subject to minimum thermal distortion, and to be-capa'ble of machining to precise dimensional standards, which materially enhance the result secured.

The composite construction is so contrived as to harmonize with the general principle of the invention. The annulus 16 being'a' concen tric unit with the standard structure and both being solids of revolution, the somewhat stressed condition of the annulus does not impart unbalcenter of said annulus.

anced stresses to the standards. The ideal con ment described minimizes the disturbing effectv of such internal strains as exist, and the results secured in practiceof the invention confirm the soundness of the principles underlying the construction. While it is preferred that the surfaces 27 and 28 be cones (i. e., generated by right lines), they might within the broad scope of the invention be conoids. The surfaces 29, 31, 32, and 33 can be modified variously, but simple sections devoid of flanges, grooves, or reentrant angles are to be preferred.

.Modifications are contemplated and the description given'above should be interpreted as illustrative rather than limiting.

What is claimed is:

1.'A frame for surveying instruments, comprising in combination a base plate member;

from; and standards extending upward from the base plate member, the outer and a substantial portion of the inner. surface of the standards being surfaces of revolution about the axis of said spindle. I

2. A- frame for surveying instruments of the type mounted upon'a spindle having a' vertical axis comprising in combination a base element and a standard structure integral therewith, said standard structure comprising substantially elliptical frame members connected with the base element, and arcuate brace members-connecting the same with each other and with the base element, the outer and a substantial portionof the inner surface of said standard structure being surfaces of revolution about the spindle axis. 3. A surveying instrument frame of the type including a base plate, a vertical spindle, and standards, characterized in that the outer, and

-a substantial portion of the inner surface of the faces of revolution about the spindle axis and so formed in cross section as to be devoid of reentrant angles and of substantially uniform crosssectional area.

5. A frame element for surveying instruments comprising an annulus adapted to serve as the marginal portion of a base plate, and a standard {structure formed integrally therewith, said standard structure comprising loop-shaped frame members connected with the annulus and arouate brace members connecting the loop-shaped members with each other and with the annulus;

the outer and a substantial portion of the inner surface of said standard structure being surfaces of revolutionabout an axis passing through the 6. A transit frame comprising in combination a member including a vertical spindle-and a base plate formed integrally with each other;

and a member including a threaded annulus and telescope standards formed integrally with each other, one of said members encircling the other in a state of hoop tension and the other encircled member being in a state of radial compression, the two members being threaded gether.

7. A transit frame comprising in combination a vertical spindle and a threaded hub formed integrally with each other; and a threaded annulus and telescope standards formed integrally with each other, said annulus being in threaded engagement with said hub,'in a state of hoop tension sufllcient to preclude separation of the 8. transit frame comprising in combination a vertical spindle and a threaded hub formed integrally with each other; and a threaded annulus and telescope standards formed integrally and a substantial portion of the inner surface of said standards being surfaces of revolution both concentric with said annulus and with the axis of said spindle.

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